We report four children aged 11-18 1/2 yr first seen 7-14 yr after the diagnosis of insulin-dependent diabetes. At presentation, all had marked short stature, two had hepatomegaly, and the older three had delayed adolescence. They had been severely underinsulinized. Initial funduscopy demonstrated only occasion microaneurysms in two children and a single intraretinal hemorrhage in another. The youngest was normal. Improved control required large increases in insulin dosage. Growth rate improved significantly and hepatomegaly regressed. Puberty progressed rapidly in two older patients with poor final height. Paradoxically, with improved control, retinopathy progressed rapidly with appearance of multiple microaneurysms, nerve fiber layer infarctions, intraretinal microangiopathic changes, hemorrhages, exudates, and macular edema in all the patients and severe proliferation changes in three. One child with proliferative retinopathy in both eyes developed vitreous hemorrhage and blindness in one eye. Two required panretinal photocoagulation with no further progression of their retinopathy. These rapidly progressive retinal changes remain unexplained. We advise caution when correcting metabolic derangements of diabetic patients who have been poorly controlled for a prolonged period.